This invention relates to a system for controlling flow of temperature control fluid in a temperature control system and, more particularly, to a three-way solenoid valve in an injection system for actuating flow control valves to control temperature control fluid flow.
Most internal combustion engines employ a pressurized cooling system to dissipate the heat energy generated by the combustion process. The cooling system circulates water or liquid coolant through a water jacket which surrounds certain parts of the engine (e.g., block, cylinder, cylinder head, pistons). The heat energy is transferred from the engine parts to the coolant in the water jacket. In hot ambient air temperature environments, or when the engine is working hard, the transferred heat energy will be so great that it will cause the liquid coolant to boil (i.e., vaporize) and destroy the cooling system. To prevent this from happening, the hot coolant is circulated through a radiator well before it reaches its boiling point. The radiator dissipates enough of the heat energy to the surrounding air to maintain the coolant in the liquid state.
In cold ambient air temperature environments, especially below zero degrees Fahrenheit, or when a cold engine is started, the coolant rarely becomes hot enough to boil. Thus, the coolant does not need to flow through the radiator. Nor is it desirable to dissipate the heat energy in the coolant in such environments since internal combustion engines operate most efficiently and pollute the least when they are running relatively hot. A cold running engine will have significantly greater sliding friction between the pistons and respective cylinder walls than a hot running engine because oil viscosity decreases with temperature. A cold running engine will also have less complete combustion in the engine combustion chamber and will build up sludge more rapidly than a hot running engine. In an attempt to increase the combustion when the engine is cold, a richer fuel is provided. All of these factors lower fuel economy and increase levels of hydrocarbon exhaust emissions.
To avoid running the coolant through the radiator, coolant systems employ a thermostat. The thermostat operates as a one-way valve, blocking or allowing flow to the radiator. Most prior art coolant systems employ wax pellet type or bimetallic coil type thermostats. These thermostats are self-contained devices which open and close according to precalibrated temperature values.
Practical design constraints limit the ability oft he coolant system to adapt to a wide range of operating environments. For example, the heat removing capacity is limited by the size of the radiator and the volume and speed of coolant flow. The state of the self-contained prior art wax pellet type or bimetallic coil type thermostats is typically controlled only by coolant temperature.
The goal of all engine cooling systems is to maintain the internal engine temperature as close as possible to a predetermined optimum value. Since engine coolant temperature generally tracks internal engine temperature, the prior art approach to controlling internal engine temperature control is to control engine coolant temperature. Many problems arise from this approach. For example, sudden load increases on an engine may cause the internal engine temperature to significantly exceed the optimum value before the coolant temperature reflects this fact. If the thermostat is in the closed state just before the sudden load increase, the extra delay in opening will prolong the period of time in which the engine is unnecessarily overheated.
Another problem occurs during engine start-up or warm-up. During this period of time, the coolant temperature rises more rapidly than the internal engine temperature. Since the thermostat is actuated by coolant temperature, it often opens before the internal engine temperature has reached its optimum value, thereby causing coolant in the water jacket to prematurely cool the engine. Still other scenarios exist where the engine coolant temperature cannot be sufficiently regulated to cause the desired internal engine temperature.
When the internal engine temperature is not maintained at an optimum value, the engine oil will also not be at the optimum temperature. Engine oil life is largely dependent upon wear conditions. Engine oil life is significantly shortened if an engine is run either too cold or too hot. As noted above, a cold running engine will have less complete combustion in the engine combustion chamber and will build up sludge more rapidly than a hot running engine. The sludge contaminates the oil. A hot running engine will prematurely break down the oil. Thus, more frequent oil changes are needed when the internal engine temperature is not consistently maintained at its optimum value.
Prior art cooling systems also do not account for the fact that the optimum oil temperature varies with ambient air temperature. As the ambient air temperature declines, the internal engine components lose heat more rapidly to the environment and there is an increased cooling effect on the internal engine components from induction air. To counter these effects and thus maintain the internal engine components at the optimum operating temperature, the engine oil should be hotter in cold ambient air temperatures than in hot ambient air temperatures. Current prior art cooling systems cannot account for this difference because the cooling system is responsive only to coolant temperature. A solution to the problems associated with prior are cooling systems is disclosed in U.S. Pat. Nos. 5,467,745, 5,669,335, 5,507,251 and 5,657,722 which all disclose an improved temperature control system for controlling flow of temperature control fluid (e.g., coolant) in an internal combustion engine. These systems utilize an electronically controlled valve, (e.g., hydraulic, pneumatic, solenoid, stepper motor or thermostatic valve). The valve is controlled according to selected data in order to achieve optimum heating and cooling of the engine.
In one embodiment disclosed in those patents, hydraulic fluid is channeled through two solenoids for opening and closing a hydraulic valve. Referring to FIG. 1, a valve V is shown mounted to an internal combustion engine E. The valve V has two solenoids S1, S2 mounted on its housing, which control hydraulic fluid flow into and out of the housing. FIG. 2 is a partial cross-sectional view of one embodiment of the valve V showing fluid channels between the solenoids, S1, S2 and the valve V. One solenoid S1 controls flow of pressurized oil along an external fluid line F1 from an oil pan OP to the valve V. The second solenoid S2 controls flow from the valve back to the oil pan OP from the valve V along a second external fluid line F2.
In U.S. Pat. No. 5,638,775, an alternate hydraulic fluid injection system was disclosed wherein the solenoids were mounted to a housing which is separate from the valve. The system again utilizes two separate solenoids and external fluid lines between the valve and the oil pan.
Testing has shown that in very cold temperature conditions, fluid in external fluid lines can thicken and become difficult to pump. Also, the use of two separate solenoids is not the most cost effective way of controlling fluid flow to a valve.
A need, therefore, exists for an improved solenoid system for controlling hydraulic fluid flow to an engine temperature control valve.
A solenoid assembly is disclosed for controlling flow of hydraulic fluid from an engine to an electronic engine temperature control valve. The solenoid assembly includes a housing for mounting to an engine. The housing includes first and second fluid channels that are formed in the housing and spaced apart from one another. The first fluid channel is adapted to communicate with a high pressure internal supply flow path formed in the engine. The second fluid channel adapted to communicate with a low pressure internal return flow path formed in the engine and is in fluid communication with a hydraulic fluid reservoir. The first and second fluid channels communicate with an internal cavity formed in the housing.
A fluid outlet port is formed on the housing and is designed to be connected to an external fluid line for supplying fluid to an electronic engine temperature control valve.
A three-way solenoid valve is removably engaged with the housing. The solenoid valve has a shaft that includes at least three ports. A first port which is located within the housing and in fluid communication with the first fluid channel. A second port is located within the housing and is in fluid communication with the second fluid channel. A third port is located within the housing and is in fluid communication with the fluid outlet port. The solenoid valve is adapted to receive electrical signals for controlling flow through the ports.
The foregoing and other features and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments thereof, as illustrated in the accompanying figures.